The present invention relates generally to medical devices for protecting a patient from embolization during cardiovascular procedures. More particularly, the devices comprise a filter for temporary placement in a patient""s vessel, and an aspiration tube communicating with a portion of the filter, e.g., a reservoir tip at a vertex of the filter, for aspirating embolic material, including air and gas.
Aspiration catheters are frequently used during surgical or interventional procedures for removing thromboembolic material, e.g., air, fluid, thrombi, calcium, atheromatous plaque, and/or tissue debris, from a patient""s body cavity. During cardiovascular procedures, such as coronary artery bypass grafting surgery, ventricular septal defect repair, heart valve repair or replacement, ventricular myomectomy, aortic aneurysm repair, or aortic thrombectomy, removal of thromboembolic material from a cardiac chamber and/or the aorta is important since distal embolization may result in ischemia or infarction of peripheral organs, particularly the brain.
Endovascular techniques have been used widely as an effective and reliable alternative to surgical intervention in selected patients for treatment of vascular stenosis. It is well recognized that one of the complications associated with endovascular techniques is the dislodgment of embolic materials generated during manipulation of the vessel, thereby causing occlusion of the narrower vessels downstream and ischemia or infarct of the organ which the vessel supplies.
Several arterial and venous filters have been designed for entrapment of embolic debris generated during surgical or endovascular procedures. An aspiration catheter is often required for complete removal of embolic debris. Current aspiration catheters are designed to remove fluid and tissue debris in a body cavity. Removal of air, however, is difficult because the air bubbles tend to accumulate against the vessel wall at a position difficult to reach. Thus, removal of embolic material is often not complete and patients remain at risk for air embolization.
Thus, there is a need for devices and methods which are capable of capturing and effectively removing embolic material within a patient""s body tissue or cavity during surgical or endovascular procedures.
The present invention provides an intravascular filter for temporary placement in a patient""s vessel, such as an artery or vein. In a first embodiment, the filter comprises a porous material arranged in a generally conical shape having a base and a vertex. The base is expandable and collapsible. A reservoir tip is located at the vertex of the cone for collecting filtered embolic material. The tip also communicates with a distal end of an aspiration catheter. In certain embodiments, the reservoir tip comprises a nonporous material, e.g., latex. In other embodiments, the distal end of the aspiration tube extends only to the outer edge of the filter, e.g., the point of insertion into the vessel.
In another embodiment, the filter is mounted on a cannula, and the aspiration tube extends proximally within the cannula. The proximal end of the aspiration tube communicates with a vacuum pump.
In another embodiment, the filter is mounted on an insertion handle, and the aspiration tube extends proximally within the insertion handle. The aspiration tube includes an infusion port at the distal end for infusion of fluid, such as saline or heparin.
In another embodiment, the filter is mounted on a distal end of an obturator, and the aspiration tube extends proximally within the obturator. The distal end of the aspiration tube may further include a turbine which extends into the reservoir tip for removing large embolic particles.
The present invention further provides occluding devices for temporary placement in a patient""s vessel, such as an artery or vein. In a first embodiment, the device comprises a nonporous material arranged in a conical shape having an expandable base and a vertex. A reservoir tip is located at the vertex of the cone for collecting filtered embolic material. The tip also communicates with a distal end of an aspiration catheter. In certain embodiments, the device is mounted on an insertion handle, having the aspiration tube extending proximally within the handle. Alternatively, the device is mounted on a cannula or an obturator.
The invention also provides methods for protecting a patient from embolization using the filter or occluding devices described above. During cardiopulmonary bypass, for example, the filter or the occluding device is placed in a collapsed state and inserted into the patient""s aorta. The filter or the occluding device is expanded to capture embolic material, including air, fluid, thrombi, calcium, atheromatous plaque, and/or tissue debris. The proximal end of the aspiration catheter is connected to a vacuum, and emboli are aspirated under negative pressure and removed from the aorta. The filter or the occluding device is then collapsed and removed from the aorta.
It will be understood that there are several advantages associated in using the devices and methods disclosed herein for preventing embolic complication during cardiovascular procedures. For example, (1) the filter is adapted for temporary placement in a patient""s artery or vein; (2) the filter communicates with an aspiration tube for removal of embolic material; (3) the filter includes capability, such as a turbine or infusion port, for breakup of large embolic particles; (4) the occluding device provides aortic occlusion during cardiopulmonary bypass in addition to providing protection from distal embolization; (5) using the occluding device in place of an aortic clamp minimizes vascular injury caused by the clamp; and (6) the devices remove air and gas in addition to particles liable to cause distal embolization.